Scanning and cleaning linework for adult coloring book pages. 2015-12-01

Drawing coloring book pages is wonderful fun, but do you dread the work at the end to turn it into something you can sell and share? Do your pictures come out pixelated or gray or just not as great as the original artwork? Here are some tips and guidelines for getting the most out of your artwork, most easily. I am using Photoshop for my examples (CS3), but these tools are also available in Photoshop Elements, and in Gimp, which is free editing software. I am presuming a basic amount of familiarity with the program, and we are sticking with raster images; converting images to vector is a whole new ballgame.

Before you scan

Before you scan the artwork, take a close look at it. Have you erased all of the pencil lines? Are there any places where you didn't get your lines to quiiiite meet? Taking a little cleanup time on the original before you scan can save you a lot of time later.

Make sure your scanner is clean, too! A hair or eraser rubbing or smudge can mean having to do more work later, or having to re-scan altogether.

Scanning

Set your scanner to between 300 and 600 dpi -- any more will take a lot of file space and time, but not gain you anything in print quality. Use grayscale or color, not bitmap or black and white! Although it is easy to think of your inkwork as black and white, the truth is, there is a tiny gradient at the edge of each inked line, and when you lose this, your work starts to look choppy and less smooth. The white paper may scan in a little gray or yellow, but this is simple (and better) to adjust after we scan.

Place your artwork on the scanner neatly, with the edge of the art along one of the straight edges of the scanner, sitting inside the lip, if your scanner has a lip. Press down as you are scanning, or put a book on the lid if your artwork has any buckle or is in a sketchbook, so that the artwork is pressed tight up against the glass.

If you are scanning a piece of artwork larger than your scanner, it is especially important to scan with a lot of overlap, and make sure that the artwork is straight for each scan. I have an article on stitching scans here.

Saving (part 1)

I like to save this file - not touched up or altered in any way! - as a raw base. Every time you make changes to your piece, you lose precious information. Sometimes, you may find that you make too much of a change, or crop something important out, or your file is too small, or you otherwise regret your edits. It's nice to be able to go back to the original scan and have something to start over with, without having to scan again. (Especially if you've sold the original!)

Do not save this as .jpg! Jpeg format, though it is useful because everyone can view it, is a lossy file format - it compresses every time you save it, and is often not up to printing standards. My preference is for .tif files, or .psd (Photoshop). These are high-quality file types that can be opened and saved without losing information.

Cleaning: Levels and Line Quality

The first thing to do to your file is truth the white. I do this before re-sizing for print size because I find that cleaning it at a larger size gives you better end quality. Start by enlarging your canvas size. This changes the size of your file without enlarging the artwork itself, and gives you a pure white border around your artwork to compare with. You will undoubtedly notice that your background was not white, even if it appeared white before!

If you scanned in color, it is a good idea to change your mode to grayscale at this point (Image > Mode). Do not simply try to jump to black and white! You will lose a lot of precious fine detail. The easiest way to whiten your background is to adjust your contrast - but this is also the clumsiest. In Photoshop, the preferred method is to use levels. These are found under Image > Adjustments > Levels.

When you first scan, your levels may look something like this:

The three slider bars indicated by the triangles at the bottom let you define where the pure white (right triangle), pure black (left triangle), and perfect middle are. Move the right slider to the left and you can watch your gray background disappear. If your black lines look a little gray, move the left slider to the right to darken them up. You can also adjust the middle level to get your artwork as clean and true to the original as possible.

(Pro tip, courtesy of Selina Fenech: You can press the alt key while viewing your levels to show the true blacks and whites within your document!)

Zoom in to your artwork 100% and make sure you have the preview box checked when you're making any adjustments like this. Anything you can see on the screen at 100%, you will be able to see when you print.

If you open up levels again, your graph is likely to look quite different. You've removed a lot of extra information from your file.

If you scanned in black and white, adjusted your levels too much or otherwise notice that your lines are a little ragged looking at the edges (and you can't go back to the original scan for some reason), you can fix that using levels, too! This is an example from Maigan Lynn's well-named piece, Lots and Lots of Hair, from Fishpond Fantasies:

The first thing to do is blur your piece slightly. Under Filter > Blur choose Gaussian Blur, and adjust it with the preview on until the edges are sufficiently fuzzy. (I find that 2 pixels works well for many of my files, but it will depend on your resolution.)

But ew, it's blurry and looks out of focus! So open up levels, previewing the piece at 100% zoom, and experiment with the sliders until the lines look clean and nice.

Now we have lines that look deliberate, without any lost information, blurriness, or scatter.

Cleaning: Extras

You might notice some lines right along the edge of your scan. This is scanner burn, and frequently occurs at edges or places where the paper wasn't sitting tight to the scanner glass. It's easiest to miss around the edges, so zoom in (ctrl +) and make sure that you either erase those lines with an eraser, select the edge with a rectangular select tool and delete, or crop the artwork so that all of those lines go away completely.

Zoom in throughout the piece, looking for weird marks from the scan, pencil marks you forgot to erase, stray hairs, and other little flaws. Delete things with an eraser, or use a fine pen tool to connect lines that didn't quite make it.

Saving (part 2) and Sizing

You've done the work, your file is all cleaned up! Now, the final thing to do is resize the file for your needs and save it.

I usually work on 9 x 12 paper, so my artwork is just a little bit bigger than the paper I print on. I like to save a large version of my art, so that I can use it for other things in the future. When you resize something, you can make it smaller without losing quality, but you can't make it bigger without enlarging every flaw. I save this large version as a .tif or .psd file, and name it, for example, ellenmillion-amazingartwork-large.tif

Then I resize the image to 8x10.5, to fit on a letter size page with comfortable margins, and save that version as ellenmillion-amazingartwork-letter.tif or ellenmillion-amazingartwork-print.tif. Remember to maintain your aspect ratio when you resize. If you need to, crop your artwork to fit the area, or add some whitespace to fill the space. Otherwise, your artwork will look stretched or warped. I usually add white margins to my page, so that my file is 8.5 x 11 inches exactly, and I can see on the screen how it will look on the paper.

With that file safely saved, now you'll want to make a version of the artwork to share online. This should be something that can easily be viewed online, no more than 1000 pixels on the long side, and no less than 650. Before you save this as a .jpg and release it to the world, add a watermark! At the very least, your name should be on it somewhere, and even better would be your webpage address, so that when your image gets shared, that information goes with it. (How to watermark is its own article... maybe my next one?)

Now, often, when you save your .jpg file, you are saving a copy, and when you go to close Photoshop, you'll be asked if you want to save your changes to the ellenmillion-amazingartwork-print.tif. Don't do it! You will overwrite your big beautiful print file with your small image, good only for viewing online. If you want to be extra safe, as soon as your print file is cleaned up and the right size and saved, change the file to read-only so you can't ever accidentally lose it with a careless save.

Closing Comments

Remember that your final audience is someone who is going to be scrutinizing your artwork at a very detailed level. They will be tackling your linework with tools of color, and staring at each line and blank space - maybe even longer than you did! It is worth the time and effort to make a clean file that will print beautifully, and make someone's coloring pleasurable and memorable.

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